According to the study, presented Tuesday at the American Chemical Society national meeting in San Diego, no harmful side effects were noted.

How green coffee bean extract, which is sold as a supplement in the United States, contributes to weight loss is unclear. But study author Joe Vinson, a chemist at the University of Scranton in Pennsylvania, theorizes a chemical in the unroasted bean called chlorogenic acid could be responsible.

Researchers still recommend dieters to exercise and follow a healthy diet. The study was small and more research on the extract's effects is needed. A larger study of about 60 people is planned, according to Vinson.